1. Field of the Invention
This invention relates to a wire seal for sealing a gap between an electrical wire and a cavity of a waterproof electrical connector.
2. Description of the Prior Art
In an electrical connector, a terminal secured to one end of an electrical wire is inserted in a cavity of a connector housing. A wire seal formed of an elastic material has conventionally been employed for sealing a gap between the cavity of the connector housing and the wire. The prior art has provided the following arrangement for this purpose. A cylindrical wire seal is previously fitted with the end of the wire and crimped thereto. The terminal is then inserted into -the cavity of the connector housing through its one open end and the wire seal is press fitted into the open end of the cavity to close a gap between the wire and the inner peripheral face of the cavity, thereby providing the waterproof seal.
In the above-described arrangement, the wire seal is cylindrical so that the wire is inserted therethrough, and the wire seal has a lip portion formed on its outer peripheral face. The wire seal possesses elasticity at the region thereof where the wire is fitted to the wire seal. The elasticity acts toward the inner periphery of the wire seal. The wire seal further possesses elasticity at the region thereof press-fitted to the open end of the cavity. This elasticity acts toward the outer periphery of the wire seal.
The wire seal is subjected to a hydraulic pressure higher than a normal pressure when a high-pressurized water or liquid is applied to the connector for the cleaning thereof or when an automotive vehicle in which the connector is employed runs in muddy water at a high speed. In such a case, the water sometimes invades the connector housing. The water enters through the gap between the inner peripheral face of the housing cavity and the wire seal rather than between the wire and the wire seal. The reason for this is that the wire seal is fitted with the wire end before the wire seal is press-fitted into the housing cavity, as described above, and the wire seal is allowed to deform to expand outwardly when it is fitted with the wire end. Accordingly, the inner diameter of the cylindrical wire seal can be set at a value sufficiently smaller than that of the wire without lowering an efficiency of the work for fitting the wire seal with the wire, so that a relatively large sealing force can be achieved between the wire and the wire seal. On the other hand, the outer diameter of the wire seal needs to be reduced to its minimum in view of an efficiency of the work for press-fitting it into the housing cavity so that a force required for the press fitting is rendered as small as possible. Consequently, a sufficient sealing force cannot be obtained between the inner peripheral face of the housing cavity and the wire seal.